More shooting problems

in a book i have i found a way to shoot things with a limit of them on the screen. The problem is , i think, the way i am referencing them. When i make them visible all the time only one of them works, and the others just stay at the top.

maxMis = 10;
for (i=0; i<maxMis; i++) {
    attachMovie("missile", "missile"+i, i);
    missile = _root["missile"+i];
    missile._visible = false
    missile.fired = false;
}
onEnterFrame = function () {
    for (i=0; i<maxMis; i++) {
        missile = _root["missile"+i];
        onMouseDown = function () {
            if (!missile.fired) {
                missile.visible = true;
                missile.fired = true;
                missile._x = _xmouse;
                missile._y = _ymouse;
            }
        };
        if (missile.fired) {
            missile._y -= 10;
            if (missile._y<0) {
                missile._visible = false;
                missile.fired = false;
            }
        }
    }
};

does anyone know why? Or a different way to reference them